Manatee River: Rye Wilderness Park to Fort Hamer is a 7 mile trail located near Bradenton, FL. The trail is primarily used for canoeing and sea kayaking.
I canoed this river a few years ago, I remember there was a couple of rope swings, saw a pretty big gator and a dam at the end(going east). All in all it's a nice paddle had a good time and there was no one else there so had the hole river to ourselves!
Love this trail, almost never anyone on it. The red trail is very sandy but fun to walk. There is even a camp ground that is available for weekends.